Array Gain of a Nested Array in Spatially Uncorrelated Noise

Spatial resolution will be improved with the increment of the aperture in array signal processing. In order to obtain high resolution, a large number of sensors are needed for the uniform linear array (ULA), resulting in the high hardware cost and computational complexity. Therefore, using fewer sensors to achieve the same half-power beamwidth as ULA and to suppress grating lobes has an important application value in underwater acoustic engineering. In this paper, the nested arrays (NA) are introduced for achieving similar performance to the ULA with fewer sensors. A multiplicative beamforming method of the NA is proposed, and a coherent processing technique is presented for improving the array gain (AG). The performances are compared with the beam patterns of the ULA and NAs using conventional beamforming method and the proposed multiplicative beamforming method. Through the coherent product processor, the AG is improved by the coherent integration of signals and the incoherent suppression of noise. Through simulation results, it can be concluded that a small NA with P+Q-1 sensors can yield an AG as high as that of a large ULA of PQ elements.